1. Field of the Invention
The present invention relates in general to hand-held devices and in particular to motorized tape measures.
2. Prior Art
Measuring tapes are well known in the art. An elongated flexible strip or tape of material having measuring indicia thereon is wound on a spool in a housing. Materials consist of cloth like materials, plastic or metal for the tape. Some measuring tapes with plastic or metal tape having measuring indicia thereon are wound on a spool that is associated with a spring. This spring is wound by pulling the tape from the spool in the housing and the wound spring retracts the tape upon release of the tape.
A drawback with this type of device is that it requires one hand of the operator to be used to hold the housing and the other hand of the operator to be used to pull the tape from the housing.
Another drawback with this type of device is that prevention of movement of the tape is typically done by manually engaging a lock mechanism.
A further drawback with this type of device is that the spring used to retract the tape into the spool pulls the tape at a very fast and uncontrolled speed allowing the end of the tape to strike the housing. These quick strikes against the housing can cause tape breakage.
A variety of power-movement tape measures have been disclosed in prior art that drive the tape out of the housing or into and out of the housing. Also, a variety of movement prevention or braking of the tape devices have been disclosed. These power-movement tape measures have complex reduction mechanisms in the drive systems. Furthermore, these power-movement tape measures have limited ability to resist tape movement when the motor is deactivated. A need exists to lower the complexity of the reduction and drive mechanism. This mechanism drives the tape on and off the spool, of a power-movement measuring tape. To accomplish this reduction in complexity, the need exists to reduce the number of components. This reduction in components is done by eliminating the need for drive belts, holes in the tape with engaging sprockets, tensioners with electronic feedback, clutches, drive rollers, recoiling springs or guide rollers opposed to the force of drive rollers.
Another need exists to provide resistance to tape movement for ease of use and to prevent the tape from uncoiling and getting jammed in the housing. This need is when the power-movement measuring tape is deactivated and activated. A further need exists for regulating the speed of the tape reduction into and against the housing to prevent tape breakage.
In order to provide background information so that the invention may be completely understood and appreciated in its proper context, reference may be made to a number of prior art patents as follows:
U.S. Pat. No. 5,875,897 to Pullen discloses a power-movement tape measure that only drives the tape off of the spool. This is done through a retention mechanism that consists of a motor output shaft driving gear, a step gear, a small gear and two pressure rollers one of which is driven by another gear. The retraction of the tape onto the spool is accomplished by a pull rod disengaging a pressure roller from the tape against a spring member. In this prior art, retraction of the tape is by a coiled spring and not controlled by the motor. Additionally, an embodiment also driving the tape off of the spool is disclosed by drive belt and three pulleys. A pull rod for disengaging the belt is also included.
U.S. Pat No. 5,768,797 to Trevino discloses a power-movement tape measure that drives the tape off and on the spool by a motor driving a friction roller through a complex planetary gear system. The prior art also states that the planetary gear system allows slippage between the reel and the drive motor. Additionally, a microprocessor is used for motor direction control.
U.S. Pat. No. 5,471,761 to Cheng discloses a power-movement tape measure that has the tape being slightly wider than the groove in the annular reel. This width is for keeping the tape from moving on the annular wheel. This prior art also discloses a gear train engaging the inner teeth of the annular reel for driving and the external teeth of the annular reel, which is used for braking. A brake pad is also toothed and movable into and out of contact with the annular reel by a switch coupled with a linkage.
U.S. Pat No. 5,48,837 to Han-Teng discloses a power-movement tape measure that has the tape being driven by a frictional pressing roller and guide roller. These rollers are meshed between a small gear and external toothing around an outside wall of an annular wheel holding the tape. This frictional pressing roller engages the tape for driving by a linkage attached to a gear train holding frame. No resistance is given in the retraction onto the spool. An additional gear train system is included to drive the spool by engagement to an inner wall of the spool.
U.S. Pat No. 5,440,820 to Hwang discloses a power-movement measuring tape that has a gear mounted on the output shaft of a motor engaged into a second gear slightly offset of center. This offset gear is mounted on a rod This offset second gear is then engaged to the inner toothed section of an annular reel. No provision is made for prevention of tape uncoiling. Additionally, protruding induction dots on the tape are included to trigger a block out device that feeds back to stop the motor.
U.S. Pat No. 5,386,643 to Corcoran discloses a power-movement measuring tape that has an equally spaced series of holes in the tape with a sprocket for driving the tape. Further disclosure states an option of a brake arm and brake pad engage to prevent rotation of the reel and disengagement to allow rotation of the reel.
U.S. Pat No. 5,044,089 to Petkovic discloses a power-movement measuring tape that is driven by a sprocket engaged in holes in the tape. Additionally, this prior art discloses one motor to extend the tape out and a second motor to retract the tape.
U.S. Pat No. 4,551,847 to Caldwell also discloses a power-movement measuring tape that is driven by a sprocket engaged in holes in the tape. Additionally, a gear train connects the motor to the sprocket and a belt is used to connect the reel to the gear train.
U.S. Pat No. 4,186,490 to Quenot discloses a power-movement measuring tape that is driven by a driving wheel engaging the tape, a speed reducer having a low speed shaft and a high speed shaft with an electric motor coupled with the high speed shaft of the reducer. A sifting pinion is also included coupled with the low speed shaft of the reducer. The pinion is shiftable between a first position in which it is coupled with the tape driving wheel and a second position in which it is coupled with the winding drum. Another disclosure of this prior art shows the driving wheel directly engaging the tape with a speed reducer having a low speed shaft and a high-speed shaft. This high-speed shaft of the reducer is again coupled with an electric motor. In addition, coupling of the low speed shaft of the speed reducer with both the driving wheel and the spool are also disclosed. A high-speed shaft and a low speed shaft are used in both cases. Furthermore this prior art discloses at least one flee roller and spring for preventing the tape from uncoiling. It can be readily seen that with only one fee roller and spring the tape can uncoil in areas not under the free roller and the embodiment shows four ball bearings with springs.
U.S. Pat. No. 5,294,066 to Lacour discloses a power cable spooling and unspooling device that shows a motor speed and rotation direction controlled by a tensioner giving feedback to the motor. Braking is applied by supplying power to the motor, which is connected, to a reel.
U.S. Pat No. 4,494,707 to Niibori discloses an apparatus for winding and unwinding an elongated flexible member, such as a window screen, by a frictional traction device. Furthermore, a clutch operatively the driving device from the winding rod during the unwinding operation.
U.S. Pat. No. 4,189,107 to Quenot discloses a coilable rule with automatic recoil with a motor and reduction mechanism within a hollow hub coaxially with the spool. Options are given for a two-stage reducer with a toothed belt, a two-stage planetary gear train and a two-stage epicyclic gear train A brake lever is locked so the tape can no longer be pulled outwards.
U.S. Pat. No. 5,245,761 to Walder discloses a manual-movement measuring tape with a braking device shiftably mounted on the housing movable into and out of engagement with the serrated edges of the spool.
As stated before, many manual-movement measuring tape braking devices are disclosed in prig art. U.S. Pat. No. 4,489,494 to Duda, as an example, discloses a typical slide actuator mounted on the housing engaging the tape as a braking device.
Whatever the precise merits, features and advantages of the above cited references, none of them achieves or fulfills the purposes of the present power movement measuring tape.
Accordingly, it is the principle object of the present invention to provide a lower complexity reduction mechanism that drives both extension and retraction of the tape.
It is another principle object of the present invention to prevent jamming of the tape in the housing from tape uncoiling when the motor is deactivated, retracting the tape and extending the tape.
It is a further principle object of the present invention to regulate the retraction of the tape speed.